21680431 has 4 divisors (see below), whose sum is σ = 22209264. Its totient is φ = 21151600.

The previous prime is 21680419. The next prime is 21680443. The reversal of 21680431 is 13408612.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21680419) and next prime (21680443).

It is a cyclic number.

It is not a de Polignac number, because 21680431 - 2¹³ = 21672239 is a prime.

It is a super-2 number, since 2×21680431² = 940082176691522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21680396 and 21680405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21680231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 264355 + ... + 264436.

It is an arithmetic number, because the mean of its divisors is an integer number (5552316).

Almost surely, 2^21680431 is an apocalyptic number.

21680431 is a deficient number, since it is larger than the sum of its proper divisors (528833).

21680431 is an equidigital number, since it uses as much as digits as its factorization.

21680431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 528832.

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 21680431 is about 4656.2249730871. The cubic root of 21680431 is about 278.8405755782.

The spelling of 21680431 in words is "twenty-one million, six hundred eighty thousand, four hundred thirty-one".